Building a Low-Cost Greenhouse

Eventually, almost everyone who grows tropical plants comes to the conclusion that it would be very nice indeed to have a greenhouse to move their tropical plants into in winter. Not only is winter protection very desirable, but a greenhouse also extends the blooming season and helps the plants get an earlier start in spring. Yes, a greenhouse would be nice, but surely it would cost too much and take too much expertise to set up. Wouldn’t it?

Not at all. Greenhouses come in every conceivable size and price range. In the end what they do is trap the energy of sunlight inside a room that quickly warms up in response. There are more ways than one to achieve this, and they aren’t all expensive, nor do they require expert construction skills. This article will take a look at the subject of greenhouses, and make some suggestions for those of you who may be ready to take the plunge.

At the top end of the price range, there are very beautiful and functional greenhouse units that can be purchased fully equipped and installed on your property by a contractor. We’re not going to talk about those. If you’re interested in one of these, you can acquire catalogs from a number of suppliers and start your search. Some of the information below will still be of interest to you, because whether your greenhouse costs $50,000 or $500 it still needs to be able to accomplish many of the same tasks.


The Very Simplest Greenhouse Frame
One-Inch PVC Pipe Bend into a Hoop

This article will focus on “do-it-yourself” or “my-spouse-will-do-it-for-me” type greenhouses. You can build a surprisingly functional greenhouse with materials that are not expensive and are easy to work with. Home Depot and other similar home supply stores have most, if not all, of the materials you need. Since there are so many variations and so many individual circumstances, we are not going to try to give a step-by-step manual like we did with the drip system a few months ago. Rather, we will take a look at the features that any greenhouse needs to include and a few nice-to-have options as well.

One other note: This article is not about greenhouses for places where snow loads are high. That is a special circumstance that requires good design and materials that can take heavy snow loads. You can still have a home greenhouse in snowy areas, but unless you are an expert at construction, you probably will need to have a contractor build your greenhouse according to the needs of your area. This article is for greenhouses in areas that have some winter freezes, perhaps an inch or so of snow from time to time, but not blizzards and several feet of snow each winter. If you need a greenhouse for heavy snow loads, contact a company that supplies these types of greenhouses to obtain one that fits your locale.

Where To Start?

First, let us consider size. If you live in an area that is heavily regulated by zoning or subdivision rules, you should check those before you build the greenhouse only to have someone complain that it is too big or too high or not allowed at all. Assuming you are good to go, then how big a greenhouse do you need? It is a rare person who builds a greenhouse and then finds that it is too big for their needs. The opposite is almost always the case – your plant collection will rapidly grow to fill it, and you will be looking for more space. So, the best thing to do is to build as big a greenhouse as you can in the space you have available or build it with the idea that you will add onto it as needed. Greenhouses are wonderful additions to a home property and can provide many hours of pleasure while the weather outside is rotten and cold. Build it as big as you dare!

What to Build The Frame Out Of


A PVC Greenhouse Frame

There are three main types of materials used for building greenhouses at home. These are:

  1. PVC Pipe:

    Yes, common PVC pipe that is used in irrigation systems makes a fine frame for a small greenhouse. It is cheap, easy to work with, has all sorts of available connecting pieces to accommodate almost any design, and is lightweight. The light weight can be a problem in high wind areas because the greenhouse can blow away. So in windy areas, the plastic covering may need to be removed during the stormy summer months to help prevent this.

  2. Wood:

    Stronger and more stable, but also more expensive unless you have access to cheap wood. A wood-framed greenhouse requires some basic carpentry, and it helps if you have some basic power tools and a little experience working with wood.

  3. Metal:

    The strongest and longest lasting material for the frame. This would seem to be outside the reach of most people, but in reality, it’s not. There are several suppliers that provide pre-drilled metal parts, including all connectors for constructing even small greenhouses at quite a reasonable price. This is a very good option for those who want to have a somewhat larger structure, say 24 feet wide by 48 feet long or bigger.

 


A Metal-Frame is Best for Large Greenhouses

The Floor

The greenhouse floor does not have to be totally flat nor do you have to grade a perfectly horizontal surface for it. I have had greenhouses on the side of a hill and they still work just fine. It is easier to build the greenhouse “square” if the surface is level, but if you cannot make a level location, you can still build your greenhouse. A slight slope inside the greenhouse is actually beneficial because excess water will flow more quickly out of the greenhouse.


Prepping a Greenhouse Floor

We should really call this the “floor” rather than the “foundation”. It is not at all necessary to pour a concrete foundation for a greenhouse. Water run-off is always an aspect of having a greenhouse full of plants. If there is a concrete floor, the water cannot sink into the ground and must find some other way to exit the greenhouse. If you must have a concrete floor, then think through how the excess water is going to be removed from the greenhouse.

If building on the ground, lay a layer of weed barrier cloth directly on the ground, cover it with an inch or two of gravel and finish it with a second layer of weed barrier cloth on top of the gravel. This will allow water to sink into the earth, and prevent weeds from growing in the greenhouse. It also provides a decent surface for walking and working. You could skip one or both layers of weed barrier and just put down the gravel, but that is not a good solution unless the budget is too tight to do it any other way.

The Covering


Polypropylene or “Poly” Covering

Greenhouses are mainly frames covered with some sort of material that allows light to enter. The frame is the main structure, and determines the strength and shape the greenhouse will take. The covering is mostly for keeping the warm air inside and barring the cold air from entering. It is not load-bearing and is usually cheap and flexible.

Greenhouse polypropylene is the least expensive material we recommend for your greenhouse. “Poly” is graded by how many years it is expected to last in the full sun, and by how thick it is. Four-year, six mil (mm) thick poly is ideal for most greenhouses. This can be purchased in many widths and lengths from horticultural and agricultural supply companies, and of course just about anything can be ordered from online suppliers. There are also many types of rigid material that provide excellent insulation and yet still let light through. These are good for side walls and can be used to cover an entire greenhouse although they are much more expensive than flexible poly (also called greenhouse film by some suppliers).

One of the main considerations, when designing the greenhouse and choosing a covering, is rain. Rain water must be able to run off the top and sides of the greenhouse. For example, if a greenhouse is built with a flat roof and covered with flexible poly, that will be a disaster when it rains. Rain water is heavy! It weighs 2 pounds per quart. Once rainwater starts collecting in any hollow or depression in the poly, its weight will stretch the poly and create big sagging sections full of water that can’t escape. The important thing to remember is that all surfaces covered with poly must be angled so that water will flow off the surface and not collect on it. This is one of the main reasons that “hoop” greenhouses are so popular – the round shape sheds water very well. A-frame type greenhouses also work well to shed water.

Doors and Windows


Unattached Side Poly Rolled up in Summer

Besides allowing entrance to the greenhouse, doors and other openings in the greenhouse are crucial for allowing heat to escape. Greenhouses are very efficient at retaining heat while the sun is shining. The temperature in a fully closed greenhouse on a warm sunny day can reach 125°F (52°C), a temperature that is dangerous to both plants and people. Ideally, the greenhouse temperature will be kept under 100°F (38°C) and most plants grow best below 90°F (32°C). Doors and windows are the cheapest way to keep the greenhouse reasonably cool.

Another method for creating windows is to leave the side wall material unattached to the ground around the bottom of the greenhouse. Instead, cut the side wall material extra long and leave it lying loosely on the ground so that it can be rolled up and tied up during hot days. This allows air to enter and exit and helps remove excess heat. During the winter months, the excess side wall material can be held tightly to the ground with cinder blocks or other heavy material.


Simple Roof Flaps to Fold up or Down

Heat rises, so a way to let it out of the top of the greenhouse is always a good idea. Cutting simple roof flaps is one way to let heat out. Another way is automatic window openers that are set to open windows at a specific temperature and close them when the temperature drops. These do not require electricity but work on the principle of expansion and contraction of certain materials as they heat and cool. As the material expands it pushes the window open, and as it contracts it allows the window to close. Of course, you can manually open and close windows as well, but whenever it is possible to automate something in the greenhouse, you will find that it is helpful to do so.

Water

All greenhouses need water for the plants. It can be from a hose, or you can easily run some PVC pipe into the greenhouse. Working with irrigation parts may seem daunting, but it is actually very simple and straightforward. All the parts are available at home supply stores and all you do is glue them together.

Heat

Greenhouses are heated by the sun any day it is shining and even when it is cloudy. However, a cold and cloudy day may not allow for enough heat to be generated to keep the greenhouse as warm as you would like. Nights are the bigger problem since inside a greenhouse the temperature will drop to within a couple of degrees of the outside temperature a few hours after dark. That may be sufficient for areas where the nights never get below 30°F (-1°C), but for most people, some greenhouse heating is worth considering. Both electric and propane/natural gas greenhouse heaters are available to do the job. Due to the high humidity, the sunshine, and temperature swings inside a greenhouse, we have found it best to use heaters intended for greenhouses because they hold up better.

Some Optional Goodies for the Greenhouse

Over time greenhouses tend to be improved upon as the people who use them figure out what is important to them. You can start growing hibiscus in the basic greenhouse described above. It provides for warmth and water and that is what it is all about! But below are some of the goodies you may want to add as you work with your greenhouse.


Wooden Tabletop on Cinder Blocks
With Drip Water System

Tables for Plants:

Tables are great – they raise the plants to a warmer air zone, keep them out of water runoff with the potential for spreading disease, and make it much easier for the normal person to work on the plants without having to stoop or bend over all the time. Tables can be made yourself. Make table tops out of 2×4 wood frames with 1×6 wood slats, and use cinder blocks for the table legs. Plastic waterproof tables are available from many sources as well.

Drip System with Timer:

Nothing frees up the plant lover like a drip system operated by a timer. This is by far the best way to water hibiscus so that the watering is regular and uniform and does not flood the pots. Try it, you’ll like it!

Wall Fans:

One of the best ways to maintain air flow through a greenhouse during warm weather is to install one or more big box fans into one of the walls of the greenhouse. These blowouts, not in, and the pressure they create draws fresh air in from the windows and doors that are left open.


Horizontal Air Fans

Horizontal Air Fans:

These are installed high up in the greenhouse and are intended to keep a gentle current of air circulating inside the greenhouse. This helps prevent fungal diseases and also mixes the air so that the greenhouse does not end up with hot and cold layers of air during the night.

Evaporative Cooler:

Often installed at the same time as the Wall Fan, the evaporative cooling system is built into the wall opposite the fan. It consists of water dripping down special material that is collected in a gutter and recirculated. When the fan is on and the water dripping fresh air is drawn through the wet material where it is cooled 15-20 degrees. The fan draws this humid cooler air through the greenhouse and out the opposite side. This “fan and pad” system will turn a 105°F (41°C) day into an 85°F (29°C) day inside the greenhouse – a great improvement in summertime heat!

Roll up Side Walls:

Available in both powered and manual versions, these walls can be rolled up during hot days and lowered at night where they fit snuggly into a ground level track to prevent air leakage.

Grow Lights:

Grow lights are not a real necessity for most parts of the world where hibiscus are grown. However, if you live in the far north or where clouds obscure the sun much of the time, adding HID or the new LED type grow lights to the greenhouse will give your hibiscus a boost when they need it most.

Insect Netting over Doors and Windows:

One of the easiest ways to control insects is to exclude them from the greenhouse with insect netting. There are now special net cloths that have holes small enough to keep out almost every known pest, including thrips which are very skinny.

Electronic Controls:

The irrigation timer is the simplest example of an electronic control. However, fancier ones can also control the heater, the fan, the pad cooling system, and any doors, windows or walls that are powered to raise and lower. In fact, electronic controls can control anything that runs on electricity, either by timers or by sensing conditions such as temperature.


Tropical Hibiscus ‘Acapulco Gold’ Blooming in a Greenhouse

The topic of greenhouses is a huge one. We are not able to cover more than the basics in this article.

Tropical Hibiscus: Wintering

For hibiscus lovers in the northern states, winter comes early, and so does the time to start figuring out how best to protect our hibiscus plants through the cold months. The most important consideration for tropical plants like hibiscus is staying warm in winter. Heat is more important than light or anything else, so let’s take a look at some good ways to provide heat to hibiscus in winter.

First and Foremost ~ Hygiene

First, before you do any moving, thoroughly wash your hibiscus. It is best to wash them several times before moving them inside, to make sure no stray pests have hopped onto them. Moving hibiscus is stressful to the plants, and any stress makes it harder for hibiscus to fight off pest attacks. Plus, indoor environments are cozy and wonderful for certain pests, like the obnoxious spider mite. So wash, wash, wash your plants to make sure you leave all pests outside. Spray every plant thoroughly with a strong spray of water, all sides of every leaf, stem, and branch. You don’t need soap or anything else, just water and lots of it. Wash your plants once or twice a week for 2-3 weeks before moving your plants inside. Then on the last washing, add horticultural oil to your water. It’s easiest to just pop a hose-end spray bottle onto your hose. Spray the plants heavily and thoroughly with the horticultural oil and water, then move them inside as soon as they dry on the last washing day.

Second ~ Don’t Stop Fertilizing!

If you stop fertilizing your hibiscus over the winter, they will go more deeply into dormancy and decline, and it will be much slower and more difficult to wake them up in the spring. It is very important to keep fertilizing through the winter months. If you use a Special-Blend Fertilizer, you will naturally water less in the winter, so you will naturally also use less fertilizer, which is perfect for your hibiscus. If you use a timed-release fertilizer, it will release more slowly in colder weather because the release rate is controlled by temperature. Your hibiscus is less actively growing and metabolizing in the winter, so they need less fertilizer, but they do need some fertilizer all winter long.

Overwintering in Cold Climates

Move them into the House

The place where hibiscus can stay warm without any extra cost is in your house. Although hibiscus is considered outdoor plants in the United States, in many parts of the world they are very popular houseplants, except for 2-3 months during summer when the pots may be set outdoors. Indoor hibiscus makes attractive, green houseplants. They help clean the air trapped inside in winter and give off extra oxygen. The greenery provides a wonderful backdrop to the drab and dreary weather of winter in many locations. And, every now and then, one of the hibiscus plants will bloom, providing a special indoor splash of color and beauty for that day.

Unless you live in Canada or northern Europe, you may not be accustomed to having hibiscus as houseplants, but they are easy to grow and quite suitable for indoor use. In the far north or any place where temperatures regularly fall below freezing during winter nights, tropical hibiscus will perish if left outdoors. Bringing them inside the house is an easy solution to overwintering them, but how best to do it?

The other main problem with placing hibiscus inside the house is finding space where there is adequate light. The closer to windows, the better for this purpose. But remember, hibiscus need warmth even more than they need light. So even if you only have room well away from windows, the hibiscus will do better there than if left outside or in an unheated garage. People have reported to us that directing just a little extra light to hibiscus in winter helps them stay green and healthy. A lamp placed nearby will help tremendously in a warm but rather dark area. What matters for hibiscus is the total amount of light they receive each day, so if the area tends to be dark you can leave a light on as much as 24 hours a day to help the hibiscus get what they need.
One of the potential problems is the size of the plants. Small hibiscus plants can grow very large by the end of summer. The simple solution to this is also good for the hibiscus – prune them back. You can reduce their size by as much as 50 percent without damaging them. More typically we cut the stems back by about 30 percent, but hibiscus is quite adaptable and will accept even severe pruning. So go ahead and reduce them to the size you need for them to fit well inside the house. Just be careful to leave some new growth and several older leaves on the plant after the pruning. Since it is winter and light are low, the hibiscus will grow back slowly, and should not grow large enough by winter’s end to become a problem in their indoor location. The idea is for them to get a head start on growing back during the slow growing season of winter, and then to rapidly grow to bloom size once they are placed outdoors in spring or early summer.

Garage, Shed, or Utility Room

If moving your hibiscus into the house is just not for you, then the next best strategy is to look for another solid structure where they can be kept over the winter. A garage, storage shed utility room, or any other structure that keeps out cold wind and provides some protection against the winter weather can be made to work. Again, the goal is to provide as much warmth as possible and at least some light to keep the hibiscus going. A structure with windows that allows sunlight to enter is ideal because the light will heat up the interior during the day and also provide the light energy needed by the hibiscus.

Greenhouses

Even inside a shelter, in some colder climates, night-time temperatures can drop well below freezing. If possible place a small heater in the structure for use on those cold nights. Even better is a heater with a thermostat that you set to go on at 40°F (4°C) or higher. Small space heaters equipped with thermostats are usually inexpensive, so this doesn’t have to be a large expense. If you can afford to keep the structure as high as 65°F (19°C) the hibiscus will thrive. But with energy costs these days that much heat may not be affordable. The idea is to find the highest temperature you can afford to maintain, then set the thermostat to that temperature. Even 35°F (2°C) will help the hibiscus a great deal compared to allowing the temperature to fall below freezing.

Buying or building a greenhouse is the ultimate way to protect your hibiscus over the winter. These are wonderful additions to a property, and a good one will provide all sorts of opportunities to enjoy hibiscus year round. Whether you build your own or order one from one of the many greenhouse companies, such structures allow for year round growth and fresh flowers if heated to at least 60°F (15°C) during the winter.

One benefit of greenhouses is that they trap the rays of the early morning sun and heat the inside of the greenhouse far more rapidly than the outside air warms up. The greenhouse also reaches a much higher temperature during the day than the outside air. For instance, on a cold sunny day in a warmer climate zone, the temperature outside might be 35°F (2°C) at dawn, 50°F (10°C) by noon, and peak at 60°F (15°C) briefly in the afternoon. Compare that to the greenhouse temperature that, if unheated at night, will also be 35°F (2°C) at dawn, but reach 50°F (10°C) by 10 AM, 75°F (24°C) by noon, and peak over 80°F (26°C) during the afternoon. Similarly, the temperatures drop again rapidly at night outside, but in the greenhouse remain warmer for many hours before eventually matching the outside temps shortly before sunrise. With a heated greenhouse, the same thing happens but in addition to the warmth of trapping the suns rays in daytime, you also help the plants by keeping the temperatures at night at 60°F (15°C) or at whatever you set the thermostat for.

In a cold climate where heating costs are very high, most hibiscus can survive if temperatures stay at or above 35°F (2°C), but warmer is better. If you can afford to keep your greenhouse at or above 40°F (5°C), it will be much better for hibiscus. Every few degrees of extra warmth will mean healthier and happier hibiscus, so find the level that you can afford. Also, consider the duration of the cold temperatures. Sustained cold temperatures that last for many hours and/or many days or weeks will do more damage to hibiscus than an occasional dip into low temperatures for a short amount of time.

The ability to trap heat inside a greenhouse is so good that on warm sunny days the temperature will rise too high – even over 100°F (38°C) on some days. You need to build your greenhouse with sufficient windows and doors so that you can allow heat to escape on sunny warm days by opening them to the outside air. The main downside to greenhouses is that they involve an investment of money and time to build. If you decide to make this investment, it will pay off in great fun and success with winter growing of hibiscus outdoors.

Get creative!

Hibiscus 'Hibiscus at Christmas'
Hibiscus Blooming Indoors at Christmas

Some hibiscus lovers use their office space to grow hibiscus during the winter months. Or perhaps a relative or friend has a suitable space where you can winter your hibiscus. Avoid using a space that is too far from where you normally spend time, because the hibiscus will need to be checked on at regular intervals, mainly for watering.

Overwintering in Warmer Climates

If you live in a warmer climate, where temperatures rarely fall below freezing, and when they do it is only for one or two nights before warming up again, then you may be able to winter your hibiscus outside by providing some simple protection measures. If your area has a history of having fewer than ten nights per year that fall into the high 20’s (-2°C) or above and no nights colder than that, you have the possibility of protecting your hibiscus outdoors.

One of the best ways to protect outdoor hibiscus that is planted in the ground is to mulch over the root zone and around the main stem of the plant. A thick layer of leaves or compost can help protect the roots and keep them from freezing at night. This goes only so far though. For more protection, wrap the entire hibiscus bush in heavy frost cloth. This can add several degrees of freeze protection for the plants. In addition, you can run outdoor Christmas lights up under the frost cloth. During cold nights the lights can be turned on and the small amount of heat they give off will add several more degrees of warmth under the frost cloth. We have seen hibiscus bushes treated this way survive winters where temperatures reached as low as the 25°F (-4°C). A fully exposed hibiscus is usually severely damaged or killed by nights in the mid-20s, but just this amount of protection will prevent most frost damage.

Potted hibiscus in areas with just a few light freezes can be protected in other ways too. The pots can be moved up next to the house which will add a few degrees of warmth for them. A south or west wall with sun exposure during the day is another good place to locate the pots. Placing hibiscus under solid overhangs or under trees with thick canopies that prevent heat from radiating out into space at night also offer cold night protection. Some people report successful protection by tipping their potted hibiscus over on their sides and covering them with tarps or frost cloth on cold nights. Running Christmas lights under the tarps would afford even more protection.

Surviving an Unexpected Freeze

If your hibiscus is caught outside and unprotected by a sudden nighttime freeze, you can take action during the night to save them. This is a bad situation to be in but does happen occasionally even in the mildest climates. It happened to us three winters ago, and we used this strategy to save our hibiscus. We keep a temperature sensor outside in the hibiscus garden that radios the temperature to an indoor display so we can monitor the temperatures the hibiscus experience. This sounds exotic, but it is actually a simple device that is widely available at garden centers, costs well under $50, and runs on batteries.

One night three winters ago, we watched in dismay as the temperature dropped to freezing, then below freezing and showed no signs of stabilizing. By midnight it had dropped to 27°F (-3°C) and there was no way to protect our in-the-ground hibiscus. We had heard that simply running sprinklers on tropical plants could protect them from a freeze, and we decided to try it since we were sure our hibiscus would not make it through this very cold night without serious damage. So we went outside and turned on all our sprinklers. Soon all the hibiscus were being sprayed by the pop-up sprinkler system that was originally installed to water the lawn. How could this help, you ask? Well, the water coming up out of the pipes below the ground is considerably warmer than freezing. As this relatively warm water fell on the hibiscus and coated them, it protected them with a blanket of warm water. However, it was so cold that night that the water began to freeze on the leaves! We watched in horror as more and more ice built up on the plants, certain that we would lose all our hibiscus. Our sprinkler idea certainly looked disastrous, but it turned out to be protective. The continuous spray of water kept the ice temperature right at 32°F (0°C) and prevented it from dropping any lower. At 32°F (0°C) for only a few nighttime hours, the sap inside the hibiscus didn’t freeze. I left the sprinklers going until the air temperature rose above freezing the next morning and the ice melted off the hibiscus. Yes, we had a wet mess in the garden, and yes we wasted some water, but most of our hibiscus only sustained minor damage from that night and grew back the following summer as if they had never been through a hard freeze. We do not recommend this technique except in an emergency! But if you are ever faced with an unexpected hard freeze and unprotected hibiscus, a spray of water from sprinklers or hose will help keep the sap from freezing and prevent serious damage or death.

Older is Better

Tropical hibiscus can be grown and kept safe through winter, even in areas where freezing weather occurs. Remember, the main principle is to provide them with as much warmth as you can along with as much light as is practical in the warm area you place them in. The older the plants are the tougher they are in winter. We don’t worry at all about our 10-year-old and older hibiscus. Their thick woody main trunk and stems are not much affected by minor frosts and freezes and they are able to grow new shoots to replace any damaged ones each summer. The biggest challenge is with hibiscus experiencing their first winter. For these plants, we recommend an indoor, warm location whenever possible. If you provide the warmth, they will repay you with much beauty and enjoyment for years to come!

Yellow Leaves on Hibiscus

“Help! The leaves on my hibiscus plant are turning yellow. What’s wrong with it?”

Don’t panic, yellow leaves on hibiscus are normal. They look like something is wrong, but they are usually just a warning, a call for help, and not a sign of impending death.

Hibiscus leaves turn yellow and drop from the plant due to stress. The stress can be of any type and figure out what kind of stress is the challenge for the gardener. We cannot tell you exactly what is wrong with the plant without knowing a lot more than you are likely to be able to tell us. YOU have to think about it, and when you are pretty sure you have determined the cause, then you can take action to relieve the stress on your hibiscus. This article is intended to help you figure it out what is wrong.

Stresses that can cause yellow leaves on hibiscus include:

1. Not Enough Water
In warm conditions, hibiscus needs a lot of water, even every day or more than once a day if it’s really hot or windy. Self-watering pots can be an excellent way to avoid this type of stress. A watering system controlled by a timer is another way for gardens with large numbers of plants.

2. Too Much Water
Yes, hibiscus can also be given too much water when the weather is cool or overcast. Hibiscus like to be moist but not sopping wet and if they don’t need the water due to cold or dark conditions then too much will stress the root system.

3. Too Hot
This is related to water but please take note on super hot summer days that hibiscus will need lots of water to keep all the big lush leaves well supplied. If they don’t get enough they react by dropping leaves (that turn yellow first) so that they don’t need as much water.

4. Too Cold
Hibiscus are tropical plants that thrive in the same temperatures that people like, 65-85°F (18-29°C). Like us, they will survive, but they will not like temperatures down to freezing and up to 110°F (38°C). If they get too cold or are placed in a cold drafty window, they can react with yellow leaves.

5. Too Much Direct Sunlight
Hibiscus like sunlight but just as most people like moderate amounts of it so do hibiscus. Too much sun places stress on hibiscus that is not used to it and they can react with yellow leaves or big white spots on leaves. The white spots are similar to sunburn on us. They won’t kill the plant but will cause it to shed leaves.

6. Too Little Sunlight
Light is the source of life for plants such as hibiscus. If they do not get enough to support all the big lush leaves they will drop some of their leaves (which turn yellow first) so that they don’t need to support so many. However, that means that there is less green chlorophyll left to support the needs of the rest of the plant so it may continue to decline until there are only a few leaves left on the plant.

7. Insects, Particularly Spider Mites
Spider mites are tiny spiders that look like little crabs under magnification. Usually, you cannot see spider mites with the naked eye but do they ever leave a mark on hibiscus leaves! First, you may see mottling of the leaves which begin to look dirty and then tired. The underside of leaves will show marks made when the mites suck the juices from the leaves. As the infestation gets worse you will see small spider webs under the leaves and at the top of stems. Leaves will yellow and fall off the plant and the entire plant will look stressed. If left untreated, spider mites can cause every leaf on the plant to fall. It takes hibiscus weeks to recover from a bad spider mite infestation so it is best to take action as soon as possible.

8. Too Windy
Most of us do not realize the stress that the wind places on plants. The Wind dries them out and the result is yellow leaves.

9. Improper Nutrition or pH ~ Chlorosis
This is a different condition, called Chlorosis and the yellow is a different yellow. The leaves will remain partly green and partly yellow when there is a nutrition problem. Leaves almost always fall off the plant after turning solid yellow. If they do not turn completely yellow nor fall off, then it is likely that the problem is a lack of essential nutrients. This can be due to no fertilizer applied or due to a pH level of the soil that is too high or too low. The leaves do not turn a bright yellow all over if this is the case nor do they drop off. Such problems can be corrected by using fertilizer and/or amending the soil with substances that will neutralize the pH. Consult a nursery professional at a local garden center if this is the case.

10. Pesticide Use
This is not a common problem but overuse of pesticide or using the wrong pesticide or too strong a pesticide or spraying in the hot sun of mid day can also cause leaf problems. If you have applied pesticide recently this may be the problem but if you used the same type at the same strength and done so in morning or evening then it is most likely one of the other stress problems above.

Once you have reviewed all the possible problems and decided on a likely source of the stress the cure is to remove the stress. Sometimes it is already done, as when you have watered thoroughly after neglecting to do so during a heat wave. There is no saving the yellow leaves that WILL fall off but the good news is that hibiscus will quickly grow back new green leaves when the stress is removed. Sometimes it becomes necessary to prune back a stem that has lost all of its leaves except for a few at the top. Pruning causes a cascade of plant growth hormones to enter the bare stem and stimulates new growth on the remaining part of the stem after pruning. This is a final solution if all else fails but it is best to remove the cause of stress first and to feed and water the plant well since that may be all it will take to get new growth on your hibiscus.

Yellow leaves are not the worst thing in the world. Sometimes the situation will correct itself, other times you need to correct the stressful condition. The hibiscus will do its part by reacting to the improved condition by no longer dropping leaves and often by regrowing new ones to replace any that were lost. Good luck with your growing and gardening and by all means have fun with it!

Spider Mites

My Hibiscus Leaves are Turning Yellow!


Yellow Leaves on an Otherwise-Healthy Plant
The First Sign of Spider Mites

Spider mites are a warm weather problem for many hibiscus growers. They prefer hot, sunny, dry conditions and their levels can soar when the temperatures rise. If not dealt with they can cause all the leaves of a hibiscus to fall off and seriously damage the overall health of the plant.

How Can I Tell if My Hibiscus Have Spider Mites?

The first sign of spider mites is yellow leaves. A leaf or two first gets yellow mottling mixed in its normal green, then slowly the entire leaf turns bright yellow. At first, you just see a few yellow leaves, here and there, and don’t think anything of them. But very soon the spider mite population explodes and more and more leaves turn yellow at an increasing rate of destruction.


Spider Mite Webs in Bright Sunlight

As the spider mites spread, they become visible to the naked eye only in the brightest light with the closest inspection. A magnifying glass helps immensely at this stage. Look at the tips of the branches with yellow leaves, and you will see very fine webbing. These are the spider mites’ webs. You can sometimes see little dots on the webs – the spider mites themselves. At this point, you have a severe infestation that must be dealt with quickly or these little pests will make every leaf on your plants turn yellow and fall off, which can eventually kill the hibiscus.

Tell-Tale Signs of Spider Mites


An Advanced Case of Spider Mites
Look Closely to See the Webs & Mites on Growing Tips
Leaves Show the Typical “Mottling” of Green & Yellow

Tiny Spider Webs: Look for tiny spider webs on the growing tips of your plants. You will need to look very closely, in bright sunlight, for very fine, tiny webs on the smallest growing tips or developing buds. If you have good eyes and bright light, you may see tiny dots along the webs. These are the spider mites. With a magnifying glass, you can see that the dots actually look like tiny crabs scuttling along the web.

Growing hibiscus in the house or in a greenhouse offers a lot of protection from many forces of nature, including pests like thrips, ants, slugs, and even aphids much of the time. However, there is one bug that thrives in the warm conditions of the greenhouse and positively flourishes in the warm, dry environment of a house – the spider mite. The warmer and drier the environment, the more these little critters reproduce! So if your hibiscus is still indoors, watch carefully for signs of them.

Stippled Leaves: Leaves become stippled as the mites pierce the leaves and draw out chlorophyll from them, leaving colorless leaf spots behind. If you start to see leaves that look like this, with yellow stippling, search for spider mite webs on the stem tips.


Leaf Stippled by Spider Mites

Yellow Leaves: If the infestation continues, leaves that are badly infested will turn yellow and fall off. For many people, yellow leaves that fall off their hibiscus is the first clue that something is wrong. But by the time the infestation reaches this stage, it is already quite advanced. It’s best to learn how to detect spider mites in the earlier stages.

Sick Plant: If the spider mite infestation continues unchecked, the whole plant begins to look tired, with the leaves slightly drooping despite being well watered.

Defoliation: If left untreated the mites can create a mass of webbing over the plants, and most or all of the leaves will become damaged, turn yellow, and fall off.

How Do I Get Rid of Spider Mites?


Plant Defoliated by Spider Mites

Over the years, we have written many articles on how to control spider mites. The methods below are the ones we have found to be most effective at killing spider mites with the least amount of harm to the hibiscus plants. The method each of us chooses depends on the circumstances – how many hibiscus plants we have, how big the plants are, whether they are indoors or outdoors, in a house or greenhouse, in pots or in the ground, etc. At HVH we have hibiscus growing in the greenhouse, on the ground in an outside garden, indoors in a house environment, and outside on porches and decks in pots. We use different pest control methods for each of these different sets of hibiscus. Very few of us have extra time to waste, so efficiency matters! All of these methods work. It’s just a matter of finding the method that is quickest, easiest, and most efficient for you hibiscus and their growing circumstances.

DROWNING SPIDER MITES

This is our favorite method for all hibiscus growing in small-medium pots and for houseplant hibiscus. You only have to do it ONCE to kill all spider mites and their eggs. It kills every kind of spider mite, even the most microscopic ones that can hide in cracks in the bark. This method does require precision and care. You’ll need a timer and a thermometer – a kitchen “candy” thermometer is perfect. If the water is too hot or you leave the plants too long, you can damage the leaves and they will all fall off after treatment. If the water is much too hot and you leave the plants much too long, you could actually kill a very young plant. But if the water is too cool or if you don’t leave the plants in the water long enough, you won’t dissolve the covers of the eggs and kill the growing larvae, which means the infestation will come right back.


A Large Sock on a Small Pot
  1. Wrap the hibiscus plant pots in some kind of fabric and use a twist tie to secure the fabric around the base of the plant. The fabric must let water through, so don’t use plastic bags, or you will carefully protect any pests that are living in the pot and soil. Large socks or pantyhose work well to wrap up small pots, and pillow cases work well for large pots.
  2. Lay several hibiscus plants on their sides, pots and all, in a bathtub. You can put many of them close together in a single layer in the bottom of the tub.
  3. Fill the tub with water that is bath water temperature – about 90°F (32°C). It should not be so hot that you can’t comfortably keep your skin in it. What feels too hot to the skin will risk damaging your plants’ leaves.
  4. Fill the tub until all the plants are covered, and weight the plants down to make sure all parts of all plants are submerged in the water. (An easy way to weight them is to cover the plants with two large towels, then to pull the two shelf racks out of your oven and lay those carefully over the top of the towels.)
  5. Leave the plants submerged in the water for 45-60 minutes.
  6. Drain out the water and stand the plants up in the tub until the excess water drains out of the pots.
  7. Remove the fabric covers, and scoop any loose soil in the fabric back into the plant pots.
  8. Leave the plants out of bright light for a few hours to rest, then put them back where they belong. Be careful not to water the plants again until the soil dries out after this thorough soaking.

Unless plants are recontaminated by exposure to another infected plant, plants should remain free of spider mites, aphids, and other pests for 4-6 months or more. This method has the added advantage of leaching out any build-up of fertilizer salts in potted plants, which needs to be done once or twice a year. So it is two plant-care activities in one.

WASHING OFF SPIDER MITES


BugBlaster

If your hibiscus is too big to put in a sink or bathtub, an alternative method is to wash your plants in a shower, under a faucet, or with a hose or BugBlaster. If done carefully and conscientiously, this method will wash off and drown adult spider mites, but it will not wash off or drown all eggs and nymphs. So you will have to repeat it 3-4 times, every 5-7 days, to get rid of all the spider mites as soon as they hatch out and grow into adults.

This method works for large hibiscus in pots or for hibiscus planted in the ground. It’s especially good for people with smaller hibiscus collections, because it is very effective, and it is the least damaging to plants and to the environment. It is time-consuming though; each plant must be washed slowly and carefully.

  1. If plants are in pots, lay them on their side where the pots can be rolled over to all sides. If plants are in the ground, get a long enough hose that you can walk all around each plant.
  2. Using a hard stream of water, wash every single millimeter of each plant – the top and bottom of every single leaf, branch, stem, and twig. Spray systematically, making sure you don’t miss one spot on the plant where spider mites could be lurking. Spider mites live mostly on the bottoms of leaves, so spraying the bottom of each leaf carefully is crucial.
  3. When finished, wash the ground with a very strong stream of water and enough water to drown any spider mites that fell off the plants.
  4. Repeat this washing process 2-3 more times every 5-7 days.

TREATING SPIDER MITES WITH SPRAYS

Another alternative method is to treat with either a miticide, such as Bayer Advanced 3-in-1 or with Horticultural Oil or Neem Oil. All three treatments work equally well, in our opinion, and we sometimes alternate between them, using one one week and the other the next week. Just like the washing method, sprays are effective at zapping adult spider mites, but in our experience, they don’t kill all the eggs or nymphs. So you have to repeat the spraying every 5-7 days for 3-4 egg-hatching cycles to make sure you get every emerging adult spider mite.

Breathing any of these products is very bad for you, so if you decide to spray, you should absolutely use a respirator mask. Oil droplets aren’t poisonous, but breathing oil into your lungs is very harmful to your body. You can feel it in your lungs for quite a while afterward if you make this mistake! It takes a lot of spraying to kill all the spider mites, and that amount of spraying without a mask is definitely bad for lungs.

One more note about spraying: All these products are best sprayed in the evening when the plant can be protected from the sun for the hours that the products are doing their work. If you spray in the evening, the products have 8-12 hours to work, and the sun won’t burn the products into plant leaves and burn them or harm them in any other way.

  1. Put your hibiscus in a protected place outside with enough space to walk all around each plant.
  2. Put on your respirator mask.
  3. Carefully and systematically spray every millimeter of the plant: tops and bottoms of every single leaf, stem, branch, and twig, as well as the surface of the pot and soil. It takes the time to spray this carefully, but you may as well not bother spraying at all if you don’t do it this carefully! Spider mites living mostly on the bottoms of leaves, so spraying the bottom of each leaf carefully is crucial.
  4. Let the spray product dry for several hours before bringing the plants back into a house.
  5. Repeat this spraying process 2-3 more times at intervals of 5-7 days.

The trick with pest control is conscientiousness. Any one of these methods will work if applied conscientiously following the directions exactly. So find the method that’s easiest and most comfortable for you to follow!

Chlorosis

Yellow Leaves ~ Is it Chlorosis?


‘Chlorotic Hibiscus Leaves’

What is Chlorosis?

The green we see in the leaves and stems of plants is a green pigment called “chlorophyll.” Chlorophyll is much more than a pretty color. It is the essential substance that a plant uses to produce food and energy from sunlight, fertilizing nutrients, and water. When all of a plant’s leaves begin to lose their green color, this means they are losing their chlorophyll, or the ability to produce food and energy for growth and flowering. “Chlorosis” is a special situation where plants have some kind of condition, such as a disease or nutritional deficiency, that causes them to produce less chlorophyll than normal.

How Can I Tell Chlorosis from other Causes of Yellow Leaves?

For our purposes, chlorotic leaves on hibiscus are those that turn yellow but do not fall off right away. Most other causes of yellow leaves result in the leaf falling off shortly after it turns yellow (spider mites, normal replacement of aging leaves with new leaves, extreme weather conditions, etc). When hibiscus leaves become chlorotic, they usually turn yellow between the veins that are visible on the leaf, while the veins themselves remain green. This gives a more mottled impression than a leaf which quickly turns yellow all over and then falls off. Chlorotic leaves will eventually turn brown along their edges, then the whole leaf may yellow and fall off, but this is a very slow process.

What Causes Leaf Chlorosis?

There are many possible causes of chlorosis. These are the causes we most commonly see:

  • Iron deficiency in the soil or potting mix
  • Magnesium deficiency in the soil or potting mix
  • High pH (above 7.2) of the soil or potting mix – or an “alkaline” soil
  • Overly wet and poorly drained soil that damages the roots’ ability to absorb minerals
  • Fungus or other pathogens that damage the roots’ ability to absorb minerals or the plant’s ability to use them

What Do I Do about Chlorosis?

First, determine the cause of your plant’s chlorosis.

  • If your plant’s soil is overly wet or poorly drained, start by correcting this and see if that solves the problem.
  • If the chlorotic leaves are at the ends of the stems, in the newest and youngest growth, then the problem is usually an iron deficiency.
  • If the chlorosis shows up in the lower leaves, the older growth, it is most likely a magnesium deficiency.

Chlorosis at the tips of branches in the youngest leaves
is usually caused by a deficiency of iron

Apply the appropriate treatment to fix the problem.

  • If the problem appears to be overly wet or poorly drained soil, then stop and correct this before trying anything else.
  • If the soil is not overly wet and it drains well, then try correcting for mineral deficiency.

How Do I Correct for Mineral Deficiencies?

Treatment involves making more iron or magnesium available to the plant. Both are used by the hibiscus to make chlorophyll, which is what makes the leaves green.

  • A quick but temporary fix can be achieved by spraying the leaves of the chlorotic plant with either iron chelate or magnesium sulfate, depending on which mineral appears to be deficient.
  • A longer lasting fix is achieved by applying iron chelate or magnesium sulfate to the soil or potting mix that the hibiscus is growing in.

Iron Chelate made with FeEDDHA

Both iron chelate and magnesium sulfate can be found in many nursery supply stores, but be careful when you look for them. Only iron chelates made with FeEDDHA are effective in all kinds of soil and potting mix. For your convenience, we have both these products in their optimum form for hibiscus available now in our HVH Online Store. Specific directions are included with the products about amounts to use and how to apply them.

What If These Treatments Don’t Work?


Magnesium Sulfate

1. Check the pH of the Soil: Testing soil pH accurately is actually a rather difficult task, best done by a lab experienced in doing so. You can check with the agriculture extension office in your county to see if they will check the pH for you, or we can recommend a lab where you can send a soil sample. Alternatively, you can purchase a pH meter, but be aware that the cheapest ones are notoriously inaccurate, and even the reliable ones require regular maintenance and the knowledge of how to use them properly.

2. If the pH of your Soil or Potting Mix is above 7.2, Treat to Lower the pH: The classic way to lower pH of soil or potting mix is to mix elemental sulfur and iron sulfate (ferrous sulfate) into it. This provides a long lasting fix for the problem and should eliminate iron-based chlorosis for 2 years or longer. The recommendation is to mix the two minerals together, half and half, then introduce them into the soil before watering them in. This lowers the pH and adds iron to the soil. Results are slower to see, but longer lasting and a more complete fix for the problem.

Lab Work – Is It Useful?

An agricultural lab will do a complete soil analysis for you that will reveal the amount of all the important nutrients contained in your soil, as well as the pH. A soil analysis usually costs less than $100 and can be helpful if you are not confident about the quality of the soil you are planting in. Another useful test that you can have done at the same time is a water analysis for agricultural purposes. This will tell you the water pH and a number of minerals in your water. The most complete picture of the growing situation can be obtained by sending some leaf samples to the lab where they will be analyzed to see if all the needed minerals are present in the leaf. This is how large commercial operations keep their plants growing on schedule, and obtaining this information can also be useful to the home gardener.

OK, so this sounds like a lot of trouble and expense to go to! We agree! We only recommend lab analysis of soil, water, or plant leaves for those with stubborn chlorosis problems, or for those with enough money, time, and interest to make the experience of working with an agriculture lab enjoyable.

Feeding and Fertilizing Hibiscus

Exotic hibiscus is vigorous growers that produce many huge and vividly colored flowers. It takes regular feeding to provide the building blocks for all this growth, color pigmentation, and strong enough wood to support the heavy flowers. There is a very limited amount of plant nutrition in a pot. There is often none at all in a potting mix made solely of peat moss, composted bark, coco coir, and perlite. The peat moss, composted bark, and coco coir are not sources of food for plants – they are simply there to secure the roots and to hold water and food for the roots to absorb. It is up to you to provide the food your plant needs.

What does Hibiscus Need?

Lots of Potassium:

Hibiscus has a voracious need for potassium – that is the third or last number in the formulas often given on fertilizer containers. Potassium assists in almost every part of plant growth and metabolism. Potassium assists in photosynthesis, the plant’s process that uses sunlight and water to create sugars for food. These sugars are then used to build every part of the plant, and hibiscus, with their complex, colorful, huge flowers need more potassium than most plants to assist in these building processes. Potassium also draws water into every plant cell, keeping each cell plump, hydrated, and healthy, which in turn makes the plant lusher and prettier, as well as more resistant to drought and disease. Potassium, amazingly, is involved in almost every type of transport in a plant, moving food, nutrients, and chemicals all through every part of the plant. The strangest thing about potassium is that it isn’t actually built into any part of the plant! It functions by floating as “free ions” through all the plant’s systems, locking into this chemical or that chemical to make this process or that process work. When a plant undergoes stress, loses water, wilts, or looks sickly, these free potassium ions can be easily lost and it is up to us to replace them with our plants. So keeping enough potassium in our hibiscus, particularly during times of heavy blooming, can be challenging. Almost no commercial fertilizers contain enough potassium to keep hibiscus as healthy as we want them to be. At HVH we had to develop our own formula to get the potassium we needed for our own hibiscus, and over time, at the request of customers, we began to offer it for sale. This is our HVH Special Blend Fertilizer – the fertilizer we developed for use in our greenhouses.

Very Little Phosphorus:

Phosphorus Toxicity
Too much Phosphorus
causes chlorotic, starving hibiscus plants
that stop blooming.

Phosphorus is another important issue with hibiscus – hibiscus does not tolerate phosphorus well, and in high doses, it will slowly damage hibiscus plants over time. One of the most common mistake novice hibiscus-growers make is to use “Superbloom” or “Bloom Booster” fertilizers. These products contain extremely high proportions of phosphorus and are very damaging to hibiscus. We did a careful trial of phosphorus some years ago at HVH, in order to find out what the optimum levels of phosphorus would be for root and flower development. We intended to gradually increase phosphorus with each watering over a period of time, expecting to find improved blooming. Instead, we watched the hibiscus go downhill within a couple of weeks of increasing phosphorus! It was shocking how quickly and how severely the phosphorus sickened our plants! As the trial continued, the hibiscus became stunted, their leaves yellowed, and they looked terrible! When we did further research on the effects of phosphorus, we found out that in several species of plants, phosphorus ties up other minerals and nutrients, such as iron, before the roots can absorb them. So our hibiscus was being slowly starved to death. No matter how many nutrients we put in their fertilizer, their roots were absorbing less and less of everything the plants needed. This was enough to convince us that hibiscus needs to be protected from high amounts of phosphorus. Bottom line – don’t use high phosphorus fertilizers claiming to be bloom enhancers! They may do something for some species of plants, but for hibiscus, they are a disaster waiting to happen.

Medium Amounts of Nitrogen:

Fertilizer Burn
Fertilizer Burn on Hibiscus Leaves
Too much Nitrogen turns the edges of the leaves brown

All living cells use nitrogen, and all plants need plenty of nitrogen. Plants use nitrogen in their proteins, enzymes, in chlorophyll, and in almost all of their metabolic processes. Too much nitrogen can “burn” leaves, the familiar “fertilizer burn” that turns the leaf edges dark brown. But too little nitrogen can bring plant growth to a halt. So the goal is to provide enough for optimum growth without overdoing it and burning the plant. For hibiscus, this means a middle-ranged amount of nitrogen.

No matter what fertilizer you use, always keep an eye out for nitrogen fertilizer burn. If you see the telltale brown leaf edges, drop all fertilizer for a couple of weeks, and water with only plain water. When you begin to fertilize again, use a weaker fertilizer solution – for example, cut your fertilizer dosage in half. Keep watching for fertilizer burn, and cut back your fertilizer until you reach the point where you can fertilize on your regular schedule and not cause any burn in your plants.

How do I Know How Much Nitrogen, Phosphorus, and Potassium my Fertilizer Has?

In the United States, the big numbers on the labels of all fertilizers called the NPK numbers, give the percentage of each of the three main macronutrients in this order: Nitrogen (N) – Phosphorus (P) – Potassium (K). (These numbers measure different things in some other countries, so check your country’s system before applying the numbers to your hibiscus care.) When looking for a fertilizer for hibiscus, look for this ratio: Medium – Low – High. If all three numbers are the same, as in most “Superbloom” formulas, there is too much phosphorus and too little potassium for hibiscus. The ratio we have found to be the best is the one we use in our HVH Special Blend Fertilizer: 17-5-24. This is the fertilizer we developed for our own hibiscus, after much trial and error. You don’t need this exact ratio, but you do need this pattern of Medium Nitrogen (N) – Low Phosphorus (P) – High Potassium (K).

NPK Chart
How to Read Fertilizer Numbers

If your fertilizer has less-than-optimum levels of potassium in it, you can supplement potassium with our HVH Hibiscus Booster. The booster is intended to supplement your fertilizer with extra potassium and nitrogen, not replace it, since it is not a complete and balanced fertilizer, and has none of the trace minerals that hibiscus need. For example, if you are using the complete HVH Special Blend Fertilizer on a weekly basis, you may want to use the Hibiscus Booster once a month during the flowering season to give extra support to the flowering process. If you use our HVH Timed-Release Fertilizerwith lower levels of potassium, you should use the Hibiscus Booster once a week (or higher doses once a month) to provide the higher levels of potassium that hibiscus need.

Check the Minor Elements

When you look for a fertilizer, also look at the “minor elements” in the formula. These are other minerals that hibiscus need in small amounts. Make sure you find a formula that includes a minimum copper, magnesium, and iron in a soluble or chelated form. Ideally, your fertilizer will contain several other trace minerals too. When it comes to fertilizer, you pay for what you get. You can buy cheaper fertilizers, but you will get a cheaper grade of each component of the fertilizer. Cheaper components may not dissolve well in water and may wash away without ever entering your plant. Or they can contain traces of harmful chemicals that can actually damage your plants. For example, some minerals are available in a chloride form for less money, and many less expensive fertilizers use these chloride forms. But repeated dosing with chlorines is very damaging to hibiscus, and the damage increases over time.

Read and Follow the Directions!

Hibiscus 'Living Legend'
A good fertilizer program makes ‘Living Legend’
grow and bloom vigorously year after year.

One more very important part of fertilizing is to very carefully follow the directions that come with any fertilizer. Hibiscus like to be fed small amounts often rather than large amounts occasionally, so the very best way to feed them is to use a half-dose of fertilizer every time you water. If you fertilize once a week, use the regular dose recommended on the fertilizer label. If you fertilize once a month or less, you can use a double-dose, but we don’t recommend this because hibiscus do best with steady and even water and fertilizer on a daily and weekly basis.

How to Fertilize

For hibiscus planted in the ground, it is easiest to hook up your water hose to a proportioner or fertilizer injector so you can water and feed at the same time. Or, if you use a drip-type watering system, fertilizer injectors are inexpensive and easy to add to your system. If neither of these methods works for you, just mix your water and water soluble plant food in a container, then water each plant well. For potted hibiscus, be sure to pour enough of the solution into each pot so that some comes out the bottom of the pot.

It’s much better for hibiscus to be fertilized when their soil is a bit moist. If the soil is too dry, the nitrogen in the fertilizer can burn the roots and damage the plants. Hibiscus don’t like to ever dry out completely anyway, so if you have a good watering regime, you shouldn’t ever have to worry about the soil being too dry to fertilize.

During the winter months when your hibiscus is not actively growing and blooming, cut your fertilizer way back. The less active hibiscus is, the less food they need. During the coldest two months of winter, you won’t need to fertilize at all. As the days get longer and warm up towards the end of winter, start fertilizing about once every other week. Then begin your full fertilizing program as soon as the early spring warmth begins, and keep it up all through the fall blooming season, backing off slowly as winter approaches.

I Don’t Have Time to Fertilize all the Time! Help!

If you are a very busy person, you may not be able to fertilize on a regular, frequent basis. For the “fertilizer challenged,” a more permanent fertilizer such as the HVH Timed-Release Fertilizer will work too. These fertilizers are mixed into the soil once every 3-4 months and release slowly over time. However, even the best of the timed-release fertilizers is too low in potassium for hibiscus. If you use one of these, even our own HVH timed-release formula, you will need to give your hibiscus an extra boost of potassium once or twice a month with a potassium product like our HVH Hibiscus Booster. Our booster is pure potassium nitrate, and you will see the almost instantaneous effects of adding it to your hibiscus – more flowers, brighter colors, and over time, stronger wood and roots.

Watering Hibiscus

To grow great hibiscus with lots of colorful blooms, they must be well watered. Watering well is simple, but can be something of a challenge until you determine the best strategies for your microclimate and situation. On this article, we will look at some of the best strategies for watering hibiscus, ones that have proven over time to bring about the best results.

Basic Considerations

Hibiscus are water-loving plants. They have lots of large leaves, and the blooms are big and full of moisture themselves. In the tropical areas where hibiscus originated, mostly islands or coastal areas, the air is humid and rainfall is plentiful. Most of us are not growing our hibiscus in the tropics, so we need to simulate as much as possible the natural conditions where hibiscus originally developed. That means plenty of water during the warm times of the year. Hibiscus are not built for cold temperatures and don’t know what to do with too much water when it is cold. During cold weather, we continue to water, but we water quite a bit less.

There are two basic aspects to watering well. The first is how often water is applied and the second is how much water is applied. Hibiscus need to be watered often when the weather is warm, and even more when it is hot. In most locations, that means daily watering, unless sufficient rain makes watering unnecessary on a particular day. How much water to apply is determined by how much is required to thoroughly wet the soil around the roots of the plant. In a pot that is easy to determine, but for plants in the ground it is harder. If the hibiscus is growing well, with lots of green foliage, you can assume it is getting sufficient water.

The quality of tap water is an issue in some areas. The pH (acidity) and the amount and kind of minerals in the water can affect plant growth. Hibiscus are fairly tolerant of variations in both these measures of water quality. They grow best in areas where the water is slightly acid (pH 5.5 to 6.5) and were dissolved minerals are low but will grow OK within a range of pH from 5.0 to 7.0 and with moderately hard water. If you know your water is outside these ranges, either very high or low in pH, or very hard with lots of minerals, consult your local County Dept of Agriculture for advice on how best to deal with local water conditions. A Master Gardeners group in the area is also a good source for advice about water quality.

How Often Should I Water?

Water Before Stress Shuts Down Growth and Blooming: However you water – whether by a hose, watering can, sprinkler or drip system – the water must be applied to the soil or potting mix around the roots dries out too much. When the plant cannot get enough water from the media it is growing in, many growths and blooming processes begin to shut down. At first, this shut down is not visible, but it is still happening and will affect the plant’s growth and blooming. If allowed to continue, the hibiscus will visibly wilt. Once water is applied, the wilt will disappear and the leaves will once again appear green and crisp. When this happens, don’t be fooled. Yes, the hibiscus has recovered from the near-death experience, but its future growth and blooming will be affected.

Hibiscus 'Cindy's Heart'
Water more in hot weather to keep hibiscus
like this ‘Cindy’s Heart’ blooming prolifically

Watering well means not allowing wilt to happen, not even the “invisible” pre-wilt shutting down of growth and blooming processes. The biggest cause of a slowdown or stopping of blooms in summer is a lack of sufficient water when the temperatures soar. This is very typical for gardens that are watered the same in spring as in summer. What was sufficient water in spring becomes insufficient water when temperatures rise. Hibiscus can become stressed by late afternoon on hot days, even when watered in the morning. Potted hibiscus, in particular, can use up most of their water by the end of the day, bringing about a stressed condition to the hibiscus that results in a decrease, or even cessation, of blooms. The way to counter this tendency is to water twice a day or to transplant the hibiscus to larger pots that hold more water. For plants in the ground, watering more deeply can provide the extra water that the plants need to deal with the high temperatures of summer.

Water According to the Weather: Water often, but adjust how often according to current conditions. Hotter, drier, sunnier, and windier conditions dry out pots and soil more quickly. Cloudy, rainy, cooler conditions make the water last longer. Be flexible about watering. If drying conditions are present, water more often. When wetter conditions prevail, cut back on watering. We have watered as often as three times per day when conditions called for it and cut back to once a week during rainy, cool times. Winter does not mean not watering at all. Hibiscus survive cold temperatures best if they are well watered before the cold hits. Dried out hibiscus are vulnerable to both cold and insect attack. So don’t let them become too dry! One of the better ways to help hibiscus deal with a frosty night is to sprinkle them with tap water that is well above the cold temperatures of the air.

As a general rule, water hibiscus once per day when summer temperatures are in the 70’s and low 80’s, and twice per day when they reach the upper 80’s and 90’s. If you cannot water them twice per day, then grow them under shade cloth or in larger pots that hold more water. Placing saucers underneath the pots and filling them with water will also help during the hottest times of the year. Self-watering pots are also available that contain a reservoir that sends water to the potting mix as it dries out. Drip systems run by timers are the very best way to control how often hibiscus are watered. Drips systems are not as hard to build as you may think.

How Much Should I Water?

Remember, when watering it is necessary to apply sufficient water to saturate the growing medium around the roots. When watering with a hose or watering can, be patient and water each plant thoroughly. Spend enough time watering each plant so that the water soaks all the way through the root zone and does not run off the top or out the bottom holes before soaking the root zone. An excellent way to make sure you apply enough water is to water each plant twice. The first application will soak partly through the root ball and make it easier to wet the entire root zone with the second application made shortly after the first. Flooding a pot quickly does not give the best results. Some of the water may flow from the top and the rest of it is likely to take the path of least resistance through channels the water creates in the potting mix over time and then out through the holes in the bottom. Much of the potting mix is left dry and untouched if you just flood a pot quickly once with water.

For potted plants, you can check your results by tipping a few plants out of their pots after watering. If not enough water was absorbed by the rootball, you will see a definite line where the water penetrated to and stopped. The soil will be darker above the line where it is wet and lighter below the line where it is dry. When potted plants are watered correctly the entire root ball will appear dark and wet, with no visible line between wet and dry areas. Expect a surprise when you first do this check! What seems like enough water is usually not enough to soak the entire root ball. Try it yourself until you are sure that the amount of water you are applying is sufficient to wet the entire root zone.

For plants in the ground, digging a shallow well around the base of the plant is the safest way to make sure water seeps down through the whole rootball. The well should be wider than the root ball of the plant all the way around. When you fill the well with water, the water will fall straight down through the soil, and water only what is directly under it. So it’s important for the well to cover the whole rootball and extend past it above the ground where your hibiscus will grow new roots. If you fill each well once, let it soak in, then fill it a second time, you should get the entire root zone well saturated with water.

'High Voltage' Hibiscus Plants
A drip system works best to water many hibiscus plants.
These ‘High Voltage’ hibiscus in pots are on a drip system.

By far the best way to apply the right amount of water to either pots or hibiscus planted in the ground is to set up a drip watering system that drips water into the pot or ground slowly enough that the root zone becomes wet through and through.

Fertigation – the Best Watering Technique for Healthy, Blooming Hibiscus

Fertigation means combining the tasks of watering and fertilizing into one. It can be as simple as mixing fertilizer into a watering can and using this mixture to water your hibiscus. By applying a small amount of fertilizer with every watering, your hibiscus gets a steady diet of the nutrients they need and do not experience famine and feast cycles. Having a steady and regular supply of water and nutrients allows hibiscus to maximize their potential for growth and blooming. If you have more hibiscus than can be watered by a watering can, you can buy a simple hose end attachment, often called a proportioner, that mixes fertilizer and water together as the water passes through the proportioner. All your hibiscus can be watered using the hose proportioner and receive a supply of needed nutrients with every watering. As we have described in the article on drip systems, anyone with a sufficiently large number of hibiscus can be freed from the daily watering task by using a drip system with a fertilizer injector attached to it. Each of these methods of fertigation will help you grow the most attractive, best blooming hibiscus possible.

Summary

Water often and water thoroughly for best results with your hibiscus. Combine fertilizer with the water for optimal growth and health of your plants. Adjust water according to weather conditions. If you stick with these guidelines your hibiscus will reward you with great growth and many bright and colorful blooms!

How to Build a Drip Watering System

Some say that leaky faucets led to the discovery of the benefits of drip watering. The story goes that weeds growing huge where the water dripped gave gardeners the first idea that a slow steady drip might be a beneficial way to water. Nowadays we know that leaky faucets are hard on the pocket book (continuing leaks cause a huge loss of water over time) but commercial and home growers have proven time and again that dripping water into the root zone of many plants provides the best plant performance and is the most economical way to water. Many people are tempted to give it a try, but a lack of familiarity with how to do it is what stops most from going ahead. Below we take a practical look at how and why to set up a home drip system.

Why Use a Drip System?

The why is easy. Hibiscus need a plentiful supply of water in the root zone. Plants “drink” their nutrients and minerals dissolved in the water they absorb (including fertilizer) are what plants use to grow and bloom. If Hibiscus do not get enough water during the heat of summer, they will slow down or stop both growing and bloom. They may also drop leaves so that they do not need as much water. In such a case, the plant will look OK, with some green leaves remaining, but it is likely to sit there doing nothing while we wonder what is wrong. We give it fertilizer, but still nothing. So we scratch our heads and perhaps give up. The only problem is likely to be a lack of sufficient water where and when the hibiscus needs it. Once it receives ample water, some time will be needed before growth and flowering resume, but eventually, the hibiscus will come back to life and start making glorious flowers again.

Hibiscus roots are concentrated in the first 2 feet of soil under the ground and directly below the plant canopy. Although some roots will grow further down or out to the side to find water, all you have to do to water hibiscus well is soak it into the first 2 feet of soil below the plant. A very old or large bush may benefit from deeper soaking, but for most hibiscus soaking down 2 feet will be enough. Soil dries from the top down, so by watering hibiscus a little deeper than the roots go, you encourage them to grow downward. Ideally, they will find a water source below the ground, but until this happens they are totally dependent on rain and what you provide. Different types of soils have to water according to their needs. Sandy soil will allow water penetration easily, but will also dry out very quickly. Other soils, such as what we have in our yard, are rocky and resist penetration by water. Heavy clay soils are the hardest to deal with, and usually, require some work before planting. Improving the soil in the garden by adding appropriate organic matter is always a good idea, but that is another topic for another day.

OK, you say, I realize my hibiscus plants need more water. I have a hose and will just soak them more. Actually, that is better in most cases than not watering enough, but it is not ideal. Why? Two main reasons – first it takes a lot of our precious time to soak each plant every day. In the end, it usually turns out not to be every day, and sometimes several days go by without our being able to get to it. Second, in an effort to provide enough water as quickly as possible, most of us will use the full volume of water flow available. In pots this can result in flooding the potting mix, filling air pockets and driving out the vital oxygen that plant roots need. In the ground, this style of watering often results in much of the water flowing off to the side before it has a chance to sink down into the root ball. Uneven watering – either too much or too little – is the normal result when watering with a hose.

Sprinklers are not the answer either, unfortunately. Sprinkler systems are made to water the entire surface area of a yard or garden area, but the water volume is only enough to water the top 2-3 inches of the soil. This is what a lawn needs, so sprinklers work well for lawns, and in fact, lawns are what most sprinkler systems were designed for. But in order to get water down to the bottom of your hibiscus’ root balls, you would have to run your sprinklers for several hours. For most people, before the water ever reaches the necessary soil depth, it will run off the yard onto streets, sidewalks, and driveways, never reaching the bottom roots of your hibiscus plants.

Remember, the goal is to water your hibiscus so that the water penetrates down 2-3 feet and spreads outward 1-2 feet from the main stem of the hibiscus. You can picture a column of water 2-3 feet wide and 2-3 feet deep centered under the hibiscus. A drip system will do this for you naturally. As the water drips from an emitter or similar device, it soaks in and spreads out naturally, without driving the air from the soil or potting mix. Drip systems are normally turned on and off by timers, freeing you to enjoy your garden in other ways than just watering it. Drip watering systems are suitable for potted hibiscus, too. The goal with pots is to soak the entire root ball with about 10 percent of the water draining out of the holes so that salts do not build up inside the pot.

How Much Will a Drip System Cost?

Poly Pipe for Drip System
The Basic Layout
1/2″ Black Poly Pipe Laid within 1-6′ of Each Plant
1/4″ Brown Poly Pipe Connects Each emitter to the Black Poly Pipe
Wells around plants hold water from dripper right above roots

The total cost of a complete drip system will be between $50 and $400, depending on how many plants you need to water and how automated you want the system to be. Costs vary according to what the system can or cannot do. The more flexible and convenient the system, the more it is likely to cost. However, a good basic system that can do all that you normally need to do will not cost that much. We were spending an hour a day watering our home garden by hand before installing the system, and consider that our $350 system paid for itself in a week through time saved. Even more important is the improved look and health of our hibiscus once they received enough water from an hour of dripping water each morning. The most expensive part of our system was the emitters. We bought ones that can be adjusted to emit anywhere from 0-10 gallons of water per hour. These cost about $1 each, but non-adjustable ones cost much less. Instead of using adjustable emitters to handle the different water needs of hibiscus that are much different in size, you can also use more than one emitter per plant for the larger plants. For instance, if we had bought 2-gallon-per-hour emitters, we could have used these for all the plants but then added a second emitter for medium-sized plants and a third emitter for our largest hibiscus.

To “do it yourself” you will need some parts, but all of them are available at Home Depot or Lowe’s at a reasonable cost. The main thing to remember is that each company that makes these parts does it a little differently, apparently in an attempt to force you to use their parts exclusively. Unfortunately, their strategy works. When you buy 1/2″ black poly pipe it will vary slightly in diameter according to who makes it. That means you can’t attach one brand to the other, even though both say they are half inch poly pipe. Grrr! Same with the fittings, which are the parts you use to connect extensions or side pipes to each other. My advice is to do all your drip system shopping at either Lowe’s or Home Depot and remember which one you used so you can add to the system in the future without coming up against mismatched sizes.

Of course, you can let your fingers do the walking and call a landscape maintenance company to give you a quote on setting up a system. This is obviously the easiest method and should provide excellent results. But it is much more expensive and perhaps less satisfying than building your own system. If you want to do it yourself, you will save money and really understand your system when it is up and working. It’s not hard to do, even for those with only a small amount of “do it yourself” experience.

Isn’t it Hard to Set up a Drip System?  It Must Be Too Hard for Someone Like Me!

That’s the surprising thing about drip systems! They are EASY to set up! Once you decide which hardware store to use, you’ll find all the pieces you need all together in one part of the store so even a beginner can manage to get the right parts. You can stand right there in the store and push the parts together to make sure you got ones that fit each other and come out the way you thought they would. If you’ve tried working on plumbing, can’t even manage to break open a pipe joint with a pipe wrench, and have decided that plumbing just isn’t’ for you, that doesn’t matter with drip systems! The parts just slide together without glue or tools. You don’t have to be strong or smart or know anything about plumbing. If you’re terrible at measuring and planning and drawing little blueprints (as Cindy is!), you can just buy plenty of everything and start laying the 1/2″ poly pipe out on the ground where you think you want it, then just move it around until you find a plan that works. This is the “artistic” approach to building a drip system. It may not be the most efficient way to figure your plan out, but it works just fine. Don’t let your two left thumbs and lack of mechanical, construction, or plumbing ability scare you away from this project. It’s EASY! If Cindy can do this, anyone can!

Here We Go… How to Set up a Basic Drip System for up to 150 Plants

OK, enough of the theory. Let’s get down to the nuts and bolts of how to set up a drip system. Here are the steps to use in building your own drip system:

    1. Connect Drip System to Hose Bib
      A Hose Bib (Faucet)
      The Easiest Way to Connect Your System

      Determine where you can connect to your current water supply: This can be either a hose bib (outside faucet where you connect a hose) or a place where you can cut into an existing water line. If you have no experience working with PVC pipe and water supply lines, you should just use the regular hose bib or faucet connection. You just buy a threaded connector that screws into the faucet, then push the poly pipe onto the connector. No glue or tools are needed! This hose bib connector is the first item on your list of parts.

 

    1. Drip System Layout
      The Basic Layout
      Lay 1/2″ poly pipe between plants.
      Run 1/4″ poly pipe to each plant.
      Attach drip emitters to 1/4 poly pipe.
      Dig small Wells around each plant to hold water.
      Use either drip emitters or sprinkler emitters for ground cover plants.

      Sketch a plan for the main line of water: Once you know your starting point, draw on paper (or mentally if that works best for you) a plan for laying out the flexible black 1/2″ pipe called “poly pipe” that will be the main water supply for your garden. The pipe should travel from the point of connection at the hose bib around the garden so that the pipe lies within 1 to 6 feet of each hibiscus. The layout can be circular or planned as a grid, with side pipes going off at right angles to the main pipe. The poly pipe is not very flexible but is flexible enough to make a circle over a fairly wide area. If you need it to make a hard turn at some point that is not a problem using a T or L connector which we will discuss later. The idea now is to determine how much poly pipe you will need to buy. It is usually found in 50, 100, and 500-foot lengths and does not cost much so we recommend you get the amount calculated from your drawing and then add a bit extra so you don’t run out and have to make another trip to the store.The layout of the water pipe in the garden can be anything you want. There are parts that slide into the pipe so that the pipe can be connected at various angles, go up steps, curve over arches, turn 90 degrees, and so forth. The most common of such parts are shaped like X, L. T, or Y and are hollow pieces of plastic that are inserted into the 1/2″ pipe. They are made to fit tight enough that water will not leak out, nor will the pipe pull easily from the connector, without glue or any other connection pieces. Our system consists of 250 feet of 1/2″ poly pipe with enough 1/4″ pipe and emitters connected to it to water 150 hibiscus and other plants. The main pipe is laid out in a big circle with a side pipe that extends over a jasmine-covered archway and sidewalk into another flower bed on a different side of the house. Our normal water pressure had been sufficient to water all 150 plants at one time with this system, using settings from 1-8 gallons per hour on the emitters, depending on the size of the plant. So feel free to design the system according to your needs, as almost any setup can be accommodated by this type of system.

      Drip System T-Connector
      A T-Connector at left
      An End folded back and held with an End Closer at right
      Use either drip emitters or tiny sprinkler emitters for ground cover plants.

      We did not discuss visibility of the watering pipes yet. Some people prefer that they are buried as much as possible. This is a lot more work and is not necessary if there is some type of ground cover that will hide them. Others do not mind them and after they are installed never even notice them. If you do decide to bury the 1/2′ pipe, then just dig a shallow trench (4″ deep and 4″ wide is plenty) wherever you want the pipe to be. Do not cover over the pipe until the 1/4 inch pipe is connected and the system has been tested. Covering it makes the addition of new emitters more difficult, but the benefit of not being able to see the pipe is worth it to some.

    2. Calculate how much 1/2″ poly pipe and how many connectors you need: Roughly measure off your garden and use your sketch to calculate the length of 1/2″ poly pipe you need. Make a list of the various connectors you need to create your planned line: L connectors for corners, T connectors for joining one piece of pipe into the middle of another, end closers for each end you create, stakes to anchor the pipe to the ground. It’s smart to buy more than you think you need! No matter how carefully you calculate, something unforeseen always comes up, or you somehow manage to break a part while you’re working. So calculate what you think you need, and add a bit more of everything to make sure you have what you need.
    3. Drip System Parts
      Roll of Black 1/2″ Poly Pipe (top)
      T Connector, Stake to Anchor Pipe to Ground, End Closer (left to right)
      Use these parts to lay poly pipe around the garden, between plants.

      Count your plants: Each hibiscus (or another plant) is watered by one emitter on a drip system. An emitter is merely a plastic part that allows drips of water to come out when the water pressure is within a certain range. There are many variations on this idea available but what you need to know now is that you need to buy 1 emitter for every plant that is to be watered. Count the plants you intend to water and note the number.

    4. Decide what type of emitter you want: The end point of the 1/4″ pipe can apply water in many ways. Drippers are one type of emitter. Others are called bubblers when more than a drip of water is allowed to pass through. Some are mini-sprinklers that can spread the water over a larger area, and others are sprayers that spray a small amount of water over a 45, 90. or 180-degree area. You can even attach a small diameter soaker hose to water an area of ground cover. There are many possibilities for using a drip system, but for watering hibiscus, you need to attach as an end point an emitting device that allows 2-8 gallons per hour of water to soak into the ground around the main stem of the hibiscus.
      Drip System Dripper Parts
      Spiked Dripper for Each Plant (left)
      Roll of Brown 1/4″ Poly Pipe (right)

      For our drip system, we chose an adjustable 0-10 gallons per hour dripper that come ready-made on a stake, with a built in connector to join it to the 1/4″ poly pipe, and with an included connector to join the 1/4″ pipe to the 1/2″ pipe. It’s called an “Adjustable Dripper on Spike” and it’s made by Dig Manufacturing. (See picture at right) This emitter is easy to use for beginners because you only need one emitter per plant since you can adjust the water flow, and don’t have to buy any extra connectors. They cost $1 each, so they’re more expensive than other emitters, but they work well and they’re easy connected to the system. Plus you save the cost of the 2 connectors.In order to make these emitters gather the water right over the roots of the hibiscus, we dug small wells around the base of each plant. The wells hold the water and allow it to soak down into the roots gradually.

    5. Calculate how much 1/4″ poly pipe you need: The emitters are connected to the 1/2″ black poly pipe by a smaller flexible pipe that is normally referred to as 1/4″ poly pipe. This is even cheaper than the 1/2″ pipe and available in rolls of 100′. Remember when we planned to place the 1/2″ pipe within 1-6 feet of each plant? That is because we will use the 1/4″ pipe in lengths of 1-6′ to connect each emitter to the 1/2 inch (main) water pipe. So, if you are going to water 50 hibiscus or other plants, and the average distance from the 1/2″ poly pipe is going to be 3 feet, then you will need 50 x 3 or 150 feet of 1/4″ poly pipe. In reality, you allow some slack in this pipe so would purchase 200 feet instead of the 150 feet calculated.
    6. Drip System Hole Punch Tool
      Small Tool to Punch Holes in 1/2″ Pipe

      Buy the parts: Now you’re ready to buy the parts. You’ve been making a list as you’ve gone through each step, so you should be ready to go to the store. Make a quick check of your list before you go to make sure it has all these parts:

      • connector to join the hose bib (faucet) to the 1/2″ poly pipe
      • 1/2″ poly pipe and a rough estimate of how much you need
      • T connectors, L connectors, and straight coupler connectors for the 1/2″ poly pipe
      • end closers for the 1/2″ poly pipe (they look like a double ring)
      • stakes to anchor the 1/2″ poly pipe to the ground
      • 1/4″ poly pipe and a rough estimate of how much you need (3′ or so per plant)
      • emitters (1-3 per plant, depending on what type you choose)
      • connectors that join the 1/4″ pipe to the 1/2″ pipe (if your emitters don’t include them)
      • connectors that join the emitters to the 1/4″ pipe (if your emitters don’t include them)
      • a tool that punches the correct size hole in the 1/2″ pipe so that the 1/4″ pipe fits without leaking
      Drip System Detail
      Ground Stake Pinning 1/2″ Pipe to the Ground (above)
      T Connector Joining 2 Pieces of Pipe (below)

      The tools you need are:

      • sharp pruning shears to cut the 1/2″ and 1/4″ poly pipe.
      • hammer to drive small stakes into the ground

      Getting all the parts needed is probably the hardest part of building your own watering system. Inevitably more than one trip to the store will be needed. In theory, you will get everything you need the first time, but in reality, it often does not work that well. We know one fellow who prefers to buy more than he needs and then he returns the left over parts for credit. We prefer to keep left over parts for future projects, but anyway you do it the cost is not high.

Assemble Your Drip System

  1. Put the Main Water Line Together:
    1. Start by connecting the 1/2″ poly pipe to the hose bib using the connector you bought.
    2. Then lay out the 1/2″ pipe all around your garden, between your plants, as you planned. Use pruning shears to cut each long piece to the length you want. Lay out all side pieces and extra loops you need to cover all places in your garden. Make sure your 1/2″ pipe runs within 6′ or less of all your plants.
    3. Join the 1/2″ poly pipe pieces together with plastic connectors – couplers, T’s, L’s, etc. Just push these connectors into the pipe.
    4. Anchor the 1/2″ pipe to the ground with a few stakes at strategic points, such as at ends, corners, or in the middle of long stretches. Just hammer the stake into the ground and the hook at the top will catch and hold the pipe.
  2. Flush and Close the System: 
    Drip System End Detail
    End Connector Closing End (double rings below)
    Stake Pinning 1/2″ Pipe End to Ground (above)

    Once the 1/2″ pipe is in place and connected everywhere, run the water through it to test that all connections hold and to clean any plastic debris or dirt out of the pipes so that this debris does not clog the emitters later on. When it is all flushed out and watertight, close all open ends of the 1/2″ pipe with plastic end closers. An end closer is just a set of two plastic rings. Thread the end of the 1/2″ pipe through one ring, fold the end (it’s the fold that closes the pipe), and thread it back through the second ring to hold the fold in place.

  3. Attach Emitters: Now you’re ready to attach your emitters. For each plant in your garden:
    1. Pick a spot on the 1/2″ poly pipe that is closest to the plant, and use the special tool to punch a hole in the 1/2″ pipe.
    2. Cut a piece of 1/4″ pipe long enough to reach to the plant, allowing a little extra slack.
    3. Find the connector that came with your emitter (in our case, it was attached to the emitter, and we just had to snap it off), and push it into the hole you just made in the 1/2″ pipe.
    4. Push the piece of 1/4″ pipe you just cut onto the connector to join it securely to the 1/2″ pipe.
    5. Attach the emitter to the other end of the 1/4″ pipe. If your emitter does not have a built-in connector, you will need to use a separate connector. Ours had a built-in connector and attached directly to the 1/4″ pipe.
    6. Drip System Emitter Detail
      Emitter attaches to 1/4″ pipe (left)
      1/4″ pipe attaches to 1/2″ pipe (right)
      Emitter spike is pushed into the ground

      Stake the emitter to the ground very close to the base of the plant by pushing the spike of the emitter into the ground.

    7. If your emitter is adjustable, open it a little bit by twisting the top. You can adjust the exact amount later when you get the whole system going.

    Move on and repeat this process to attach an emitter for every plant in your garden.

Turn on the water at the faucet, then adjust each emitter to get the water flow you want for each plant. When the flow is perfect for each plant, leave the water on for about an hour to water your garden. Voila! You now have a drip system!

If you have more than 150 plants, build two or three of these drip systems – one for each 50-75 plants, depending on your water pressure. Either connect the systems to separate hose bibs or use a splitter on a single hose bib to connect two systems to one bib. You can build as many drip systems as you need for the size of your yard. Most people’s water pressure can only handle watering one system at a time, so when you water, run each drip system separately.

How to Add a Timer & Fertilizer Injector to your Drip System

Control the Drip

Once you’ve built or planned your drip system, you need to decide how best to use the system. Drip systems can be controlled manually, but that is missing one of the big advantages of having such a system. It is easy to control the watering schedule using a battery powered timer and a special valve called an “electric solenoid valve.” The timer tells the valve when to open, allowing the water to flow into the system, then when to shut, cutting off the water from the system. We set ours to open for one hour in the early morning. By the time we first see the garden in the light of dawn our hibiscus are already fully watered for the day. Before this, we had to find at least an hour every day to walk around with a hose, watering each of the over 100 plants one at a time. Some days we just could not get to it, other times we felt rushed and would give each plant only the minimum amount to keep it alive. Forget to go away for a vacation! Now, with the timer activating the drip system automatically each day, we are free to enjoy the garden whenever we want without being tied to the job of watering it every day in summer.

Fertilize With the Drip System

Fertilizer Injector
Fertilizer Applicator/Filter (DIG Brand)

We all know about best intentions. Fertilizing our hibiscus is one of those jobs we all intend to do but… Fortunately, once a drip system is set up, the job of fertilizing our plants can become much easier and faster. The DIG Company offers an inexpensive addition for drip systems (available at Home Depot and elsewhere for under $15) that will handle fertilizing for you. It is not entirely automatic, but all you have to do is twist off the top of the unit and pour the HVH Special Blend fertilizer or Booster into the unit until full. Twist the top back on and you’re done! The next time the drip system is used the fertilizer will dissolve in the water as it passes through the unit, and will be carried by the drip system to all the plants on the system. This Fertilizer Unit is also a filter for the system and filters out small particles that can clog the drippers. Whether used for fertilizing or not, this unit serves an important function all the time by filtering the water that enters the drip system. It can be used with either manually controlled or timer-controlled drip systems and is we recommend it highly!

Types of Timers

Timers come in all flavors, from hugely complicated ones that can control all sorts of devices throughout a large nursery, to simple, inexpensive ones that only do one thing. This latter is what we want for a home garden. Some timers can be hardwired into the home electrical system. A few are even solar powered. But the one we use and recommend for its ease of installation and low cost runs on one 9-volt battery that lasts 1-2 years before needing to be replaced. No wiring is required! This timer activates an electric “solenoid” valve. Although these valves are available separately from timers, it is easiest to buy one that is already attached to a timer and sold as one unit. As mentioned before, these units, along with all other parts of the drip system, can be purchased economically at Home Depot, Lowe’s, or at a specialty irrigation store. Many smaller hardware stores also carry them. We purchased our DIG Model 7001 Battery Operated Irrigation timer /valve unit at our local Home Depot for less than $50.

Installation

Drip Irrigation Timer
Irrigation Timer (DIG Brand)

The installation for both the timer and the fertilizer injector/filter is easy and done at the same time. The fertilizer injector/filter comes packaged with several different types of connectors so that it can be installed in most situations without additional parts. The timer is first connected to the water source for the system, and the fertilizer injector/filter is then connected to the timer on the downstream side of the timer. The downstream side of the Injector/Filter is then connected to the drip system pipe.

To better describe the flow of water to your drip system, think of it like this – the water flows from your hose faucet or from the manual valve on a direct PVC system to the timer, then from the timer to the fertilizer injector/filter, and from there into the drip system and out the individual drippers to the plants. Along the way, fertilizer is added if you have filled the fertilizer reservoir, and all small particles are removed by the filter. It is the timer that allows the water to enter the system by opening a valve at the time you select and then closing it at the time you select to stop the flow of water.

If your system is connected to a hose faucet or to a hose, all you have to do is screw the adapters that are included into the timer, and then screw the other end of the adapter onto the faucet or hose. If your drip system is connected directly to PVC pipe, there is also a connector included with the timer that screws directly onto the pipe.

The Fertilizer/Filter unit also has adapters included that allow it to be connected directly to the timer on one end and directly to the poly water pipe on the other end. It may take some fiddling with parts to get everything connected together, but once you figure out which parts connect the system together, it is a fairly easy task to hook them up.

Install the Battery

Drip System Timer Installation
Fertilizer Injector & Timer Installed
Black Unit at top is Fertilizer Injector
(Unscrew to fill with fertilizer.)
Blue Unit at Bottom is Timer
(Blue cover opens to set the timer.)

The timer uses one 9-volt battery to operate. This battery must be purchased separately but will last for at least a year. The timer part of the timer lifts off of the lower part of the unit which houses the valve. It remains connected by a cord, but removing it allows for you to stand up or sit comfortably nearby while inserting the battery and setting up the timer. The battery compartment door is on the bottom of the timer, the side opposite the settings. After opening the battery door insert the battery into the compartment, attaching negative and positive connections to the appropriate poles. This is marked inside the compartment and described in detail in the directions that come with the timer. Close the battery door and get comfortable so you can set the timer without feeling the strain of squatting in an awkward position.

If you feel thoroughly confused by all this, don’t worry! These timers and fertilizer injectors come with excellent, clear instructions that are easy to follow. In an article like this, it’s impossible to provide instructions for every type of component you might buy. If you understand the basic concept, installing the parts will be easy.

Setting the timer

OK, we’ve now got the entire system in place. The question now is, how do we use it? The timer, consisting of a timer and a valve, is easy to set. The directions included with the timer you buy will walk you through the steps using diagrams and words that are very user-friendly. For instance, it will show you how to set the time of day you want the timer to open the valve and start the water. It then asks you how long you want the water to flow. In our conditions with the plants we have, one hour works great. Then you select the days you want the system to operate. In summer every day is best, although in rainy climates every other day may be better. There is also a button that lets you skip one day any time that button is pushed, so on a rainy day you can push that button and no water will flow thru the system until the next day. There is also a manual on and off switch that you can activate anytime that turns the system “on” for whatever length of time is already set for automatic operation. This is useful for many tasks such as checking the drippers to see if the amount of water dripping out of them is what you want.

Special Tip For Potted Plants

There is no reason not to put potted plants on a drip system. All our greenhouse plants are in pots and they all have drippers in the pot. The main difference compared to in the ground hibiscus is that most pots do not contain sufficient soil to keep them from drying out during hot summer days. Large pots almost always have large plants in them and they will get sucked dry of water just as fast as the smaller pots with smaller plants in them. So what is the solution to keeping potted hibiscus happy, growing, and flowering in midsummer? Set your timer for more than once per day. Instead of the deep soak for an hour that in the ground-plants need, use a shorter time such as 10 minutes for the system to drip water into the pots. BUT, set the timer to do this 2 or even 3 times per day, and watch the difference this will make to your potted hibiscus. University research has proven this to be the best way to water pots in nurseries, and if you try it, your results will almost certainly bear this out.

The Final Results

Hibiscus Garden
Plenty of Water Makes Plenty of Hibiscus Flowers!

Once the timer is set, watering becomes automatic. You can change this anytime you want, but until you do, the hibiscus will receive water every day that you set the timer to water them – automatically! This is the very best way to water your garden. Dripping water into the root zone for about an hour a day will make a huge difference in the appearance of your plants. We knew this from watering with a drip system in the greenhouse but were surprised at just how much better our garden plants looked and bloomed with an automatic drip system in the garden. The difference is impressive and well worth the time and cost to install the system.

We often hear people complain about a lack of blooms in midsummer, which is always puzzling because our hibiscus in the greenhouse never stops blooming, despite the extremely high summer temperatures inside. My best guess is that most people do not provide adequate midsummer water to their hibiscus and our experience with our own garden seems to confirm this. Sure you need to keep insects such as thrips from causing bud drop, and you need to keep fertilizer levels up, but by far the most important influence on the hibiscus in summer is deep, regular watering that keeps moisture available in the root zone at all times.

Sometimes people say, “The soil is moist, I can feel it, so why should I add more?” A little-known fact is that hibiscus roots can only obtain enough moisture from soil or potting mix when that soil is 50% or more saturated. When the moisture level drops below 50% saturation, the roots have to compete with the soil for the water and cannot take enough out of the soil to fulfill their needs on a hot day. Only when the level is over 50% saturated can the hibiscus roots easily obtain what they need from the moist soil. Think about a wet dishrag. When it is first wet it is almost totally saturated. If you wring it out, then you get a lot of water easily. But even though it feels moist after wringing when you squeeze it again you get at most just a few drops of water. The soil is a lot like that – there has to be ample water in it for the hibiscus to be able to get it.

Of course, there are more things you can do with your drip system now that you have it. You can add in little soaker hoses for ground cover areas, or bigger emitters for trees, or little sprinklers for grassy or mossy areas. Once you have the basic system in place and know how to add things to it, you’ll find yourself getting very creative with it. There’s nothing like building it yourself to give you the confidence to tailor it to the needs of your own yard! So have fun and good luck with your new watering system! We know you will thoroughly enjoy having a watering system in place and that your hibiscus will flourish like never before!

Planting and Potting Hibiscus

You just got your first exotic hibiscus plants, and now your first decision is whether to keep the hibiscus potted or to plant it in the ground. Hibiscus are tropical plants, so if you live in a place that freezes in the winter, the answer is an easy one – keep your hibiscus in pots that can be moved to a warm spot during winter freezes. If you live in a warm place that rarely freezes, and just barely hits 32° one or two nights per year at the most, then you have the option of planting your hibiscus in the ground. There are good reasons to keep them potted, such as being able to move them around, but we have also found that hibiscus does very well when planted in the ground in warm climates.

Planting Hibiscus in the Ground

Test your Drainage: Test the hole to be sure it drains by pouring a gallon or so of water into it. If the water disappears within an hour that is good enough. If it is still standing there after an hour you are probably planting into clay or over some other impermeable material and may end up drowning the hibiscus roots. Alternatives are to build up a raised planting bed or to amend the soil with “clay-busting” material available at most nurseries. If the hole drains well, plant the hibiscus fairly deep, covering the original root ball with a couple of inches of soil as you fill the hole.Before you plunk your hibiscus in the ground, it is important to spend a little time selecting and preparing the planting hole. Never forget the gardening wisdom of the ages, “It’s better to place a $5 plant in a $20 hole than a $20 plant in a $5 hole.” Here are two simple tests you can do to make sure you are planting into a hibiscus-safe spot:

Test Water Permeation: Test to see how well water soaks into your soil by digging a small well into the top of the ground. Fill the well with water 2 or 3 times and let it drain away for half an hour or so. Then dig into the soil, and look at the water line to see how far down the water has soaked. If the water is moist 8-10″ down, then your soil has good permeability and it’s safe to plant hibiscus in it. If only the top inch or two of the ground is moist, your soil does not have good water permeability, and your hibiscus could die of drought, no matter how much you water, because the soil resists soaking up any water you pour onto it. Before you plant your hibiscus, you will need to dig a very large hole that you fill with a high-quality planting mix, allowing plenty of extra room for the hibiscus to grow roots into.

Super Sandy Soil: If your soil is very sandy, you will probably have problems growing hibiscus in it. Very sandy soil does not absorb much water or hold fertilizer. Most of the water applied to sand flows down past plant roots, and the water that is absorbed evaporates quickly. If you have very sandy soil either grow your hibiscus in pots or be prepared to water often and use timed-release fertilizers on the surface of the soil. You can also try amending the sandy soil with good compost and other organic ingredients so that it will hold more water and fertilizer. Check with your local Dept of Agriculture and the Master Gardeners group in your area for more advice.

Digging the Hole: The hole you dig for your hibiscus needs to be a few inches wider than the plant pot, on all sides, if your soil is good. If you are amending your soil, make the hole much wider than the size of the pot. If you live in a dry place where your hibiscus could get brushed with frost and where water retention is important, plant your hibiscus deeper into the ground, with the crown of the plant, where the roots meet the trunk, right at the surface. If you live in a soggy, warm place, dig a more shallow hole to keep the crown and the tops of the roots above the surface level of the ground around the hole. The more you break up and work the ground around the hole, the more easily your hibiscus will be able to grow longer, deeper roots. So take your time, and dig a $20 hole!

Ready to Plant: Once your hole is prepared, water the hole to moisten the soil all through it before putting the hibiscus in it. Gently remove your hibiscus from its pot, being careful not to rip the roots away from the base of the plant. As tempting as it may be to pull on the plant trunk to get the plant out of the pot, resist the temptation. Instead, put your hands on the soil, and gently turn the plant upside down up in the air. Then hug the pot, and let gravity drop the plant out of the pot into your hands. Use your hands to break up the roots around the rootball a little bit on all sides, then position the plant in the prepared hole.

Look at your plant before you finalize the position. Look which way branches grow, and make sure you position in the direction that looks best from what will be the viewer’s vantage point. If the plant has listed to one side in the pot, use this replanting opportunity to make it stand up straight again in the hole in the ground. It won’t hurt the plant a bit for the roots to be put a bit sideways into the hole. Take one last look at the position of the plant, then fill it in with soil somewhat firmly, but without heavily packing or tamping it down. Water very well – deeply, 2 or 3 times to make sure it completely saturates all parts of the hole and root ball. Et Voilà! You’re done! Wait a week or two before beginning your fertilizing regime, then fertilize away. Hibiscus rarely experience transplant shock. They love to have room to spread out their roots, and you will often see a recently planted hibiscus stand up taller and look happier than it did in its pot!

 

Growing Hibiscus in Pots

Is it possible to keep hibiscus in small pots forever?

Many of us live in places where we can never put our hibiscus into the ground, and for us, the question is, “Can we keep hibiscus in manageable pots forever?” This is a question we are getting asked more and more, and the answer is, yes, you can keep hibiscus in small pots indefinitely. This is exactly what we do in our greenhouse with our own hibiscus collection. We have to keep our plants in pots that we can easily move around and fit close together in the always-limited space in a greenhouse. There are some tricks to making it work, but none of them are difficult.

How Small Can the Pots Be?

In our greenhouse, we have found that hibiscus will grow large and stay happy for many years in pots as small as 10″ in diameter. A 10″ pot is convenient because it is easy to pick up and move around, and can be put in almost any location. Any size larger than 10″ is, of course, fine too! In our houseplant testing, we are currently experimenting with keeping hibiscus in very small pots and keeping them pruned to a very compact size. So far we have been successful in smaller pots, but it is too early to tell for sure how long our plants will be happy in smaller pots. But 10″ pots have worked for us for years, and we can recommend that size with certainty.

First, Potting Medium…

If you plan to keep your hibiscus in a pot, the potting mix is very important. There are inexpensive products out there offered by mass-market sellers, but in our experience, this type of mix dooms hibiscus to a short life and poor performance. These mixes are often too heavy and hold too much water for hibiscus. They can also contain ingredients that are toxic to hibiscus. Recycled sewage sludge is often used in inexpensive mixes, and although it is sterilized, the trace mineral content is unknown and can be quite detrimental to hibiscus. Instead, what is needed is a soilless potting mix (contains no real soil) like the HVH Potting Mix. A good mix is made of coco coir, peat moss, or composted bark to hold moisture and nutrients, along with sand and/or perlite to provide more drainage. Added organic ingredients that support beneficial microbial life in the pot, such as worm castings, bat guano, or other fully composted organic material, are very beneficial in the potting mix. If you are unsure, we suggest going to the best nursery or garden center in your area and asking for a high-quality potting mix that drains well and contains some organic materials. You can always add the organic material yourself, such as HVH Worm Castings, and should ideally do so once a year in order to maintain the beneficial microbial life in the potting mix. Using high-quality potting soil for your hibiscus is a crucial step in keeping them healthy and blooming for a long time to come!

Second, Nutrition…

Hibiscus 'Simple Pleasures'

Anytime we keep hibiscus in less-than-perfect conditions, we need to maximize nutrition to help reduce the stress the plant experiences. Start with a good quality hibiscus fertilizer that has all the nutrients hibiscus need with as few contaminants as possible. Anything you put in your hibiscus pot is going to stay there for a very long time, unlike hibiscus planted in the ground. So be careful not to put anything into the pot that could possibly contaminate your hibiscus. Hibiscus prefer a light fertilizing on a frequent schedule, so if you have time to fertilize every time you water, this is the best possible way to keep hibiscus in small pots happy. Use 1/2 the dose on the fertilizer label each time you water, and watch carefully for signs of fertilizer burn – brown edges on otherwise healthy leaves. If you see signs of fertilizer burn, or “nitrogen burn,” stop fertilizing for 2-3 weeks, then use an even weaker dose of fertilizer in your regular watering. The idea is to use as much fertilizer as you can without causing fertilizer burn.

Fertilizer Burn
Fertilizer Burn ~
Burnt Edges on
Otherwise Healthy Leaves

If you can afford it, a Growth Enhancer is another option you can add to your nutritional program for your hibiscus. Growth enhancers provide different types of nutrition than fertilizers. They are loaded with the hormones and anti-stress proteins that plants themselves produce, but a plant that is stressed by a small pot may have difficulty making enough of these hormones and proteins. Supplementing with these nutrients helps keep hibiscus at optimum health levels, and gives them a break from having to produce all these proteins themselves.

One other nutritional product you may want to add to your arsenal is extra potassium, such as is found in our Hibiscus Booster. Hibiscus are voracious users of potassium, and if they become deficient in this element, their flowers will slowly diminish as size, number, and color intensity until they eventually stop blooming altogether. The more stressful the conditions a hibiscus lives in, the more potassium it needs. Tiny amounts of this inexpensive nutrient will keep your hibiscus blooming with lots of big, colorful flowers year after year.

Third, Pruning…

Pruning becomes extremely important when you keep a hibiscus in a small pot. The shape of the plant will be determined completely by how well you prune it. The more branches you encourage your plant to grow, the more it will flower since hibiscus tend to produce one flower at a time on each branch. In a small pot, you need to think about which direction the branches are growing and what kind of overall shape each branch you leave on will give your plant. If you want a branch to grow up to fill a space near the top of the plant, look for a node that is on the top side of the branch you’re pruning, and prune just above that node. This will force a branch to grow from that node up into the space you need to be filled. Try to look at each node, and imagine where a branch growing from that node will shoot out, then pick the node that looks like it will create a branch in the shape you want. It’s more of an art than a science, since we constantly turn our plants in their pots and cause sunlight to shift each time we turn them, but learning to think about these things when you prune will help you shape your potted hibiscus in ways that make it more beautiful while still keeping it more compact.

Fourth, Root Pruning…

Tropical Hibiscus 'Fat Actress'

The final step in keeping potted hibiscus happy is to prune their roots every couple of years. To check your plant’s roots, gently ease the pot off the root ball. If the roots are circling the bottom of the pot and form a solid mass at the bottom, it is time to prune them. Root pruning is easy: Using a very sharp knife that you have sterilized with alcohol or hand sanitizer, slice off the bottom 2 inches of the root ball. Then add 2 inches of fresh, good quality potting mix into the bottom of the pot, pop the plant back into the pot, water, and voilà! You’re done! As the plant grows new roots down into the fresh soil, the new roots will stimulate growth hormones throughout the plant, and the plant will produce more top growth too.

These are the basics of keeping hibiscus happy in small pots. Our greenhouse is full of very old, very happy potted hibiscus, so we know this works! Good luck to all of you with yours!

Planting Wildflowers

Wildflowers are some of the easiest and most rewarding plants to grow. They are often native to your region, require little effort and water, and provide show-stopping color year after year. They also help provide food and shelter for local wildlife, including birds, butterflies, bees and more.

Source: Planting Wildflowers